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4th grade · Math · Unit 10 of 12

Angles & Area

Acute, right, obtuse and area

What your child practices

Sorting angles into acute, right, obtuse and straight, finding area by multiplying length by width, and working backward to find a side.

Minnesota K-12 Academic Standards benchmark: 4.2.3.1; 4.2.4.1; 4.2.3.6 · lines and angles, acute, right and obtuse angles, and the area of a rectangle

How we explain it

Children can open this short lesson before they practice.

  1. Area is the space inside. Length × width for a rectangle.
  2. A right angle is a square corner (90°). Acute is smaller. Obtuse is bigger.
  3. Area is measured in square units, like cm².

Example: A rectangle is 4 cm long and 3 cm wide. What is its area? Multiply length by width. 4 × 3 = 12. Answer: 12 square cm

Angles & Area in Minnesota

In the Minnesota K-12 Academic Standards, this is unit 10 of 12 in 4th grade Math, after Fractions and before Line Plots & Data.

Gradelings describes a child's practice on this unit as Beginning, Approaching, Meeting or Exceeding (Four practice steps). That reflects practice, not a report-card mark: the teacher decides the mark.

Source: Minnesota Department of Education (MDE)

Sample questions

A taste of this unit. In the app, questions change every time and get easier or harder to match your child.

  1. Question 1

    What kind of angle is this?

    • acute
    • straight
    • obtuse
    • right

  2. Question 2

    What kind of angle is this?

    • obtuse
    • straight
    • acute
    • right

  3. Question 3

    A rectangle is 6 cm long and 8 cm wide. What is its area in square centimeters?

    answer box

  4. Question 4

    A straight line makes what kind of angle?

    • right angle
    • straight angle
    • obtuse angle

  5. Question 5

    A rectangle has an area of 45 square centimeters. It is 5 cm long. How wide is it, in centimeters?

    5 × = 45

    answer box

  6. Question 6

    Each square is 1 square unit. What is the area of the rectangle?

    • 17
    • 15
    • 16

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